The invention relates to a conduit element made of metal for uncoupling high frequency vibrations in connection with exhaust gas conduits of motor vehicle internal combustion engines.
It is known with exhaust gas conduits of motor vehicles to install in them a flexible conduit in the form of an undulating corrugated sheathing hose as an adapter, in order to absorb motions and vibrations and to uncouple them from propagation to adjacent components. Such motions and vibrations occur on the part of the elastically mounted drive machine as a consequence of load shifting reactions in normal driving operation or also on the basis of temperature-conditioned changes in length within the exhaust gas conduit. The propagation of these motions and vibrations to the vehicle should be avoided as far as possible, since the exhaust gas conduit is fastened on the vehicle floor, optionally with the interposition of elastic bracing elements.
These known adapters have a considerable length, in order to give them sufficient flexibility for accommodating relative motions between the parts of the exhaust gas conduit adjacent to them. Their rigidity, especially in the axial direction, is thus kept comparatively low, in order to prevent material fatigue and fractures resulting therefrom in the area of the adapter. Insofar as the adapters uncouple vibrations at the same time, this can consequently only apply for frequencies in the range up to about 200/250 Hz, since above this frequency range the adapters themselves are stimulated to internal vibrations. Here it can then be necessary to enclose the adapters along their undulated area by additional, vibration-damping materials in the form of metallic damping cushions or the like.
Now in the meantime, however, there increasingly arise high frequency vibrations caused on the part of the drive by the use of turbo-superchargers or compressors, which run at very high revolutions (rpm) and generate high frequency vibrations by their unbalances. In addition, owing to combustion processes associated with the opening of the discharge valves, high frequency pressure pulsations are generated in the exhaust gas elbow connecting to the motor as well as in the continuing exhaust gas installation. The known adapters are not capable of damping or uncoupling the body noise induced by these high frequency vibrations or pressure pulsations. Rather, the body noise in a frequency range of 1000 Hz to about 4000 Hz spreads beyond the exhaust gas installation and leads, chiefly in connection with housings of catalytic converters and mufflers, to the propagation of air-borne noise.